Advertise on Bikeforums.net



User Tag List

View Poll Results: What's too heavy for a set of aero wheels?

Voters
35. You may not vote on this poll
  • >2000g

    4 11.43%
  • >1800g

    10 28.57%
  • >1600g

    15 42.86%
  • >1400g

    4 11.43%
  • >1200g

    0 0%
  • >1000g

    0 0%
  • >800g

    0 0%
  • Even Lews aren't light enough for me

    2 5.71%
Page 1 of 2 12 LastLast
Results 1 to 25 of 26
  1. #1
    In beaurocratic limbo urbanknight's Avatar
    Join Date
    Mar 2006
    Location
    Los Angeles, CA
    My Bikes
    Specialized Allez, K2 Razorback
    Posts
    22,457
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    What's too heavy for aero wheels?

    At what point does a set of aero wheels become too heavy for its aero advantages in most criteriums (note, criteriums, not road races or time trials)? I noticed some of these things from the past decade weigh close to 2000g!

  2. #2
    Slow'n'Aero DrWJODonnell's Avatar
    Join Date
    Feb 2006
    Location
    Driving the pace in the crosswind
    Posts
    2,599
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Zipp 404s come in at about 1300 grams. I would not have ANY problem (and don't) racing a crit with them. However, rather than taking into account the whole wheel weight, you would really focus on the peripheral weight which is what makes it tough to accelerate. I personally would not go any deeper than a 404 (or equivalent). If you gave me 404 rims on a set of stupidly heavy hubs? I would gladly take them. Crits don't usually have a lot of climbing in them so overall weight won't be AS important.

  3. #3
    部門ニ/自転車オタク NomadVW's Avatar
    Join Date
    Dec 2005
    Location
    Yuma, AZ
    My Bikes
    2005 Specialized Roubaix Elite, 2005 Specialized FSR XC Comp, 2008 Blue T16, 2009 Blue RC8, Fetish Cycles Road Bike
    Posts
    3,172
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by DrWJODonnell View Post
    If you gave me 404 rims on ANY hubs? I would gladly take them.
    That's how I would have said it. That being said, I don't understand really the weight chasing group that aren't at a rock-bottom racing weight. I get the guys who have found that they can't go lower than XX kg without losing performance that are chasing weight savings in one area or another on the bike. But ... I mean really ... 2000 g wheels vs 1000 g wheels. 2.2 lbs. Two weeks of discipline and you can lose 2.2 lbs. It takes a month or more of disposable income (more often than not, a lot more than a month) to buy 2.2 lbs of weight savings on wheels.

    $2,000 dollar wheels are a year or more of solid coaching. My guess is the coaching will help you win more races. Anyway.... I'm just being crabby cause my ride sucked today.
    Envision, Energize, Enable

  4. #4
    Hook Em
    Join Date
    Sep 2007
    Location
    ATX
    Posts
    761
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by NomadVW View Post
    That's how I would have said it. That being said, I don't understand really the weight chasing group that aren't at a rock-bottom racing weight. I get the guys who have found that they can't go lower than XX kg without losing performance that are chasing weight savings in one area or another on the bike. But ... I mean really ... 2000 g wheels vs 1000 g wheels. 2.2 lbs. Two weeks of discipline and you can lose 2.2 lbs. It takes a month or more of disposable income (more often than not, a lot more than a month) to buy 2.2 lbs of weight savings on wheels.

    $2,000 dollar wheels are a year or more of solid coaching. My guess is the coaching will help you win more races. Anyway.... I'm just being crabby cause my ride sucked today.
    Yeah, I agree with the whole weight weenie thing, but 2.2 lbs off wheels is huge. And like others have said, since its a rotational mass, it will be far more noticeable than 2.2 lbs of your gut.
    Quote Originally Posted by rangerdavid View Post
    some people have an amazing command of the obviious.

  5. #5
    starting pistol means war YMCA's Avatar
    Join Date
    Aug 2005
    Location
    east coast
    My Bikes
    Cervelo R3
    Posts
    3,032
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by fuhrermatt View Post
    Yeah, I agree with the whole weight weenie thing, but 2.2 lbs off wheels is huge. And like others have said, since its a rotational mass, it will be far more noticeable than 2.2 lbs of your gut.
    Yes, 1kg off the bike is worth more than 1kg off the body.
    But then I never worried about weight on either end.
    I'm still riding a 58cm - 20.5 lb bike in the era of weight-weenies.
    I still weigh 195 lbs when I could easily drop 10 and with a lot more effort, 20 lbs.
    Yet, I still rock the rides and could start racing again anytime and be competitive (win) in P12's.

    Bike weight does not outweigh talent, technique, tactics, or training.
    It's just a bad way to spend the family's vacation $$$.
    I'd rather sit on a beach for a week, than buy some Zipp's, crash them and then buy some more.

    Anybody ever race those Flashpoints? 60mm of rolling thunder (1900 grams), but how do they corner? I can get them for $650 new.

  6. #6
    How much does it weigh? prendrefeu's Avatar
    Join Date
    Jul 2005
    Location
    Weight Weenie on a budget.
    My Bikes
    Lotus Fixed, Bianchi Virata 2004
    Posts
    3,427
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Have you been paying attention to the Holiday BD "Group Buy" deals? 50mm tubulars for well under $400, under 1450g, shipping included, no sales tax.
    Weight weenies keep it light.

    Director of the Midnight Express Ride; Board of Directors, Los Angeles County Bicycle Coalition.

  7. #7
    Quarq shill cslone's Avatar
    Join Date
    Jul 2004
    Location
    Ohio
    My Bikes
    08 Felt F4, 05 Fuji Team SL, 08 Planet X Stealth, 10 Kona Jake the Snake, 03 Giant OCR flat bar.
    Posts
    3,962
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I personally voted >1600. Anything above that just "feels" heavy in your hand.
    FS: Fuji SL1 frameset, 55.5cm toptube, excellent condition.

  8. #8
    Making a kilometer blurry waterrockets's Avatar
    Join Date
    May 2006
    Location
    Austin (near TX)
    My Bikes
    rkwaki's porn collection
    Posts
    26,029
    Mentioned
    19 Post(s)
    Tagged
    0 Thread(s)
    I've never believed the rotational mass thing. It's always annoyed me. Then, I remembered that I own a PowerTap

    I just lifted my rear wheel off the ground and accelerated from 36mph to 43mph holding a pedal. Over a duration of 7s, I averaged 7W. I tried to keep the acceleration slow, and I think that's a reasonable rate.

    Then, I took my tire and tube off, reducing rotating weight by 412g (WeightWeenies: 237g (tire) + 175g (tube) = 412g).

    This took the required wattage down to 5W for the same acceleration in the same duration.

    So, 412g reduction in rotating weight will save you 2W, if you can accelerate from 36mph to 43mph in only 7 seconds. That's ~0.1% of my 5s power.

    Buy nice wheels for the aerodynamics or pcad Schwag factor, not the rotating weight.

    Did I mention that I like having a power meter? I need to get with UT_Dude and his SRM to dispell the frame stiffness myth

    [EDIT] Note that the weight difference between a big tank Deep-V (580g) and a ZIPP 360 tubular (408g) is 228g. Double that for both rims and you're at 456g of savings. So it may be a tiny bit more than 2W of savings with both wheels, but it won't make up as much rotational inertia considering that the rim is not as far out from the axis as the tube and tire I removed. Certainly it wouldn't get to 3W.
    Last edited by waterrockets; 12-07-07 at 07:40 AM.

  9. #9
    Making a kilometer blurry waterrockets's Avatar
    Join Date
    May 2006
    Location
    Austin (near TX)
    My Bikes
    rkwaki's porn collection
    Posts
    26,029
    Mentioned
    19 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by YMCA View Post
    Anybody ever race those Flashpoints? 60mm of rolling thunder (1900 grams), but how do they corner? I can get them for $650 new.
    Ratebeer got some, I believe, and likes them. Best wheel deal out there, IMO. I dunno about durability record, so I'd just save them for race day and occasional training for familiarity. But, I'm done buying wheels for a while, with the PowerTap mopping up the budget.

  10. #10
    Oh The Huge Manatee Lithuania's Avatar
    Join Date
    Feb 2006
    Location
    mabra
    Posts
    4,528
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by prendrefeu View Post
    Have you been paying attention to the Holiday BD "Group Buy" deals? 50mm tubulars for well under $400, under 1450g, shipping included, no sales tax.
    wow i wasnt paying attention to this. Whats wrong with these wheels for them to be so cheap?

  11. #11
    Super Moderator
    Join Date
    Feb 2007
    Location
    Tariffville, CT
    My Bikes
    Tsunami Bikes
    Posts
    12,260
    Mentioned
    16 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by waterrockets View Post
    This took the required wattage down to 5W for the same acceleration in the same duration.
    I'm not a physicist but something doesn't seem quite right with the experiment, although I think it's great that you did it. When I find a physicist or someone who actually knows vectors and stuff I'll have to report his/her findings or explain the flaw in the experiment.

    Perhaps it is a percentage thing (5W over 7W = 29% decrease in required power)? Maybe acceleration related to time? The speeds used in your experiment? Not sure.

    It seems illogical esppecially when looking at cars. The effective savings of horsepower at the wheels of a 14 pound lighter flywheel (14 lbs vs 28 lbs stock) in a car can gain something like 100 hp depending on rpm/gear (or as little as 2-3 HP). In other words, the force required to accelerate a wheel (or a car's drivetrain) increases radically (exponentially?) with rpm. The reported "performance increase", done by alleged independent shops, finds that a light flywheel will save a lot of HP (into three digits) in first gear but by fourth or fifth gear, there is barely any difference. This is because at the higher speeds the engine cannot accelerate as briskly and so the time required to accelerate is much longer. Therefore lighter weight doesn't matter.

    Likewise but in an opposite direction, a car magazine, looking to build a low-buck140 hp or so car (handling + acceleration) did a month-to-month article of upgrades. They modded the suspenesion, engine (minor mods - exhaust, intake, etc), trying to stay within some budget or some rules. At the end of the engine "stuff" they found a measurable but small HP increase (at the wheels it went from 105 to something like 112 HP, I think about 7-8 HP increase). The next issue, in order to put big brakes on, they put 17" wheels (from 15"). Their measured HP dropped back to, or maybe below, the stock power reading. This is because the HP is measured at the tires and the larger (and heavier) wheel/tire combo ended up soaking up a lot of HP. They tried to justify this as being acceptable for the gains in cornering and braking traction but in the real world, if you look at autocrossers and drivers who regularly do laps on the track, they use smaller diameter wheels with the same width tires - the wheels are much lighter and therefore there is a corresponding increase in performance. So they'll put the 15" on for the race or laps, then the 17" for the drive home.

    Having said that, regarding the original post, wheel weight/aero requirements depend on the course. If you are racing a cross shaped hot dog course (i.e. imagine tracing a route around a plus sign), the four 180's plus four 90 degree turns will probably favor a lighter wheel, aero won't be as much a factor. If you're racing on a kidney shaped course with no turns, then aero will be more important than acceleration.

    If you're really good, you can do what Coors Light did in the early 90s - go to the front with your front and rear TriSpokes, go 35 mph for a while, and eventually blow the field apart until 4 or 5 Coors guys are together with maybe an odd rider for company. Ride away from field and let designated leader win. With an aero wheelset, no matter what the weight, if you can stay at the very front of the field, you can go through most turns at full speed. The lack of deceleration and acceleration will negate any advantage a light wheel (might) have. This happened at the second last all-road Tour of Michigan, almost all eight stages, and they did that even on a 1/2 mile course, 8 turn, narrow road, rainy and windy day.

    cdr
    "...during the Lance years, being fit became the No. 1 thing. Totally the only thing. It’s a big part of what we do, but fitness is not the only thing. There’s skills, there’s tactics … there’s all kinds of stuff..." Tim Johnson

  12. #12
    Super Moderator
    Join Date
    Feb 2007
    Location
    Tariffville, CT
    My Bikes
    Tsunami Bikes
    Posts
    12,260
    Mentioned
    16 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Lithuania View Post
    wow i wasnt paying attention to this. Whats wrong with these wheels for them to be so cheap?
    I can't speak for the Vuelta company since I have no idea who they are. Nor can I speak for the people offering the group buy.

    However, I can tell you that if you go to Taiwan and try and buy some product at the real deal manufacturer's wholesale, you will be absolutely and totally shocked.

    Remember the aluminum frames with the carbon rear triangle? They were all the craze for a while (and they're still around now I think, but prob lighter weight etc). They'd wholesale for $800-1500 from a distributor to a shop. If you went to the Taiwan show, you could pick one up for about $80-100, custom geometry, custom paint, custom decals. Just say "I'm thinking of importing them under my brand name", wait about 2-3 months, pay some customs duty and some shipping, and you have a nice new custom frame.

    Two years ago I got 4 or 5 arm warmer samples, a couple long sleeve jerseys, short sleeve jersey, and a cap from a supplier in Taiwan. Most of the quality was questionable (the word "cycling" was missing the second "c") but it cost about $8 or so for all of it. I never decided to go ahead with any of them but I wear the jerseys sometimes on the trainer.

    So, when you look at how much a component costs, it really costs very little for the product itself. Customs, shipping, and paying someone who knows English is what costs a lot. Then marketing, distribution, that all adds more. Just finding a place and making sure they're reputable will take someone a long time - visit the factory, make sure it's the same company, etc etc.

    In a group buy situation, the people offering the group buy can put a deposit down (using the initial down payment paid by the group buyers), order the stuff from their regular suppliers, wait for a few weeks for it to be made, wait a few weeks for the product to get onto a ship, wait a month for the ship to cross the Pacific, and wait a month for the product to be released from customs. They've pre-sold the stuff so they can sacrifice a bit of margin.

    Shipping costs across the Pacific are determined by volume, not weight. So it costs as much to ship one empty cargo pod as it does, say, 3000 cassettes (if they fit in the same box). If a big distributor is ordering a container or four of product and a group buy helps fill out one of the containers, it reduces overall cost per item for everything to get to the distributor. Good for them. Since it appears they have good support from the forums, they offer a nice deal to "their customers". Good for the folks that take advantage of it. Works for everyone.

    cdr
    "...during the Lance years, being fit became the No. 1 thing. Totally the only thing. It’s a big part of what we do, but fitness is not the only thing. There’s skills, there’s tactics … there’s all kinds of stuff..." Tim Johnson

  13. #13
    A Member kukusz's Avatar
    Join Date
    Aug 2007
    Location
    Denver, CO
    Posts
    855
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by carpediemracing View Post
    The next issue, in order to put big brakes on, they put 17" wheels (from 15"). Their measured HP dropped back to, or maybe below, the stock power reading. This is because the HP is measured at the tires and the larger (and heavier) wheel/tire combo ended up soaking up a lot of HP.
    I don't think this loss is due to the heavier wheel, but larger diameter wheel. The moment arm of what is pushing the car increases a lot, that causes the loss in power at the wheels. With heavier wheels on your bike, they stay the same size so the torque required to turn the wheels stays about the same.

  14. #14
    Making a kilometer blurry waterrockets's Avatar
    Join Date
    May 2006
    Location
    Austin (near TX)
    My Bikes
    rkwaki's porn collection
    Posts
    26,029
    Mentioned
    19 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by carpediemracing View Post
    It seems illogical esppecially when looking at cars.
    I see where you're going with this.

    If we were accelerating as rapidly as car engines then it would make that big of a difference. We're talking about going from 447 rpm to 549 rpm over 7 seconds, and that might be faster than in the real world. A souped up sports car engine, in 1st gear, will be going from 3000rpm to 9000rpm in about 2 seconds.

    That's 20% change in 7s vs 300% change in 2s. Can't hardly compare it.

    Then, if you look a the sports car's top gear performance, the lighter flywheel makes almost no difference... because the rev acceleration is so small (just like ours).

  15. #15
    Texas Fight! UT_Dude's Avatar
    Join Date
    Oct 2006
    Location
    Austin, TX
    Posts
    2,023
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by waterrockets View Post
    Did I mention that I like having a power meter? I need to get with UT_Dude and his SRM to dispell the frame stiffness myth
    You're on!
    T E X A S F I G H T !
    http://www.chriscollins.org

  16. #16
    Texas Fight! UT_Dude's Avatar
    Join Date
    Oct 2006
    Location
    Austin, TX
    Posts
    2,023
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by waterrockets View Post
    Ratebeer got some, I believe, and likes them. Best wheel deal out there, IMO. I dunno about durability record, so I'd just save them for race day and occasional training for familiarity. But, I'm done buying wheels for a while, with the PowerTap mopping up the budget.
    Nope. Half + off brand-name wheels through sponsorship is much better
    T E X A S F I G H T !
    http://www.chriscollins.org

  17. #17
    Senior Member
    Join Date
    Nov 2004
    Posts
    2,544
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by waterrockets View Post
    I've never believed the rotational mass thing. It's always annoyed me. Then, I remembered that I own a PowerTap

    I just lifted my rear wheel off the ground and accelerated from 36mph to 43mph holding a pedal. Over a duration of 7s, I averaged 7W. I tried to keep the acceleration slow, and I think that's a reasonable rate.

    Then, I took my tire and tube off, reducing rotating weight by 412g (WeightWeenies: 237g (tire) + 175g (tube) = 412g).

    This took the required wattage down to 5W for the same acceleration in the same duration.

    So, 412g reduction in rotating weight will save you 2W, if you can accelerate from 36mph to 43mph in only 7 seconds. That's ~0.1% of my 5s power.

    Buy nice wheels for the aerodynamics or pcad Schwag factor, not the rotating weight.

    Did I mention that I like having a power meter? I need to get with UT_Dude and his SRM to dispell the frame stiffness myth

    [EDIT] Note that the weight difference between a big tank Deep-V (580g) and a ZIPP 360 tubular (408g) is 228g. Double that for both rims and you're at 456g of savings. So it may be a tiny bit more than 2W of savings with both wheels, but it won't make up as much rotational inertia considering that the rim is not as far out from the axis as the tube and tire I removed. Certainly it wouldn't get to 3W.
    So what you're saying is that it only takes 7 watts to go from 36mph to 43mph when you're sprinting? Because if you believe that you're only saving 2 watts, then you also believe that it only takes 7 watts of power to sprint.

    Obviously it takes a lot more wattage to go from 36 to 43mph in 7 seconds. Likewise, you are going to save a lot more than 2 watts by dropping 412g. Assuming a linear curve (which it almost definitely isn't), if it took you a 500 watt increase to accelerate from 36-43mph dropping 412g would mean you'd only need a 357 watt increase to go from 36-43mph.

    Of course the relationship is far from linear so you wouldn't save 143 watts, but you'd definitely save far more than 2.

  18. #18
    Slow'n'Aero DrWJODonnell's Avatar
    Join Date
    Feb 2006
    Location
    Driving the pace in the crosswind
    Posts
    2,599
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Yoshi View Post
    So what you're saying is that it only takes 7 watts to go from 36mph to 43mph when you're sprinting? Because if you believe that you're only saving 2 watts, then you also believe that it only takes 7 watts of power to sprint.
    I believe he was saying (while his test of course has errors) that 7 watts was what it took to get the wheel to accelerate. It said nothing of the weight of the bike, rider, or aero drag. I think that by way of that, the second part of your statement also becomes invalid. Not saying the 7 watts is correct (nor was he) but I think that he knows that it takes a bit more than 7 watts to get a rider on a bike to go from 36-43mph.

  19. #19
    Super Moderator
    Join Date
    Feb 2007
    Location
    Tariffville, CT
    My Bikes
    Tsunami Bikes
    Posts
    12,260
    Mentioned
    16 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by kukusz View Post
    I don't think this loss is due to the heavier wheel, but larger diameter wheel. The moment arm of what is pushing the car increases a lot, that causes the loss in power at the wheels. With heavier wheels on your bike, they stay the same size so the torque required to turn the wheels stays about the same.
    When swapping wheel sizes in a car, the rolling diameter stays the same. In other words, the diameter of the tire is virtually identical if you get the right aspect ratio (which essentially determines height of sidewall). The diameter of the wheel is larger but the additional radius (sidewall height) of the tire is smaller. The total of the two equal that of the smaller wheel + tire combo.

    Well, that is unless you're looking to jack up the back like a dragster or put dinky wheels the hopping cars use.

    Although there isn't a similar situation in cycling, the tire's rolling diameter remained constant between the 15" and 17" wheelsets, just like between two wheelsets on a bike.

    cdr
    "...during the Lance years, being fit became the No. 1 thing. Totally the only thing. It’s a big part of what we do, but fitness is not the only thing. There’s skills, there’s tactics … there’s all kinds of stuff..." Tim Johnson

  20. #20
    Senior Member
    Join Date
    Nov 2004
    Posts
    2,544
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by DrWJODonnell View Post
    I believe he was saying (while his test of course has errors) that 7 watts was what it took to get the wheel to accelerate. It said nothing of the weight of the bike, rider, or aero drag. I think that by way of that, the second part of your statement also becomes invalid. Not saying the 7 watts is correct (nor was he) but I think that he knows that it takes a bit more than 7 watts to get a rider on a bike to go from 36-43mph.
    I'm sure he knows that it takes more than 7 watts to accelerate that much, however he said "So, 412g reduction in rotating weight will save you 2W, if you can accelerate from 36mph to 43mph in only 7 seconds. That's ~0.1% of my 5s power." which would imply that he believes reducing the weight by 412g will only save him 2 watts on his 5s power, if he could accelerate 7mph in 7 seconds.

    Clearly he would save far more than 2 watts on his 5s power if he reduced his rim weight by 412g.

  21. #21
    Super Moderator
    Join Date
    Feb 2007
    Location
    Tariffville, CT
    My Bikes
    Tsunami Bikes
    Posts
    12,260
    Mentioned
    16 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by waterrockets View Post
    I see where you're going with this.

    If we were accelerating as rapidly as car engines then it would make that big of a difference.
    I agree with you there. The tests I was thinking of were done on a engine between 2500 and 6500 rpm, so you're right, it's a big jump in revolutions (4k, or 60+% increase). And I think it's safe to say it takes about 2-3 seconds to make this jump (0-45 or so in first gear).

    In the realm of the car, 14 lbs out of 3380 is an extremely minor amount of weight. Yet it results in some measurable difference on a dyno. (Now, not being a physicist, I can't tell you what the drawbacks of the dyno are, and I'm sure there are lots of factors I don't know about with the dyno, but the measurement apparently translates into a difference in performance).

    With the bike, I'd guess my jumps are about 80-90 rpm up to 120 rpm. About a 30% jump in pedal speed, perhaps more for a slow turn - 15 mph in a 53x15 would be 50 rpm or so, and it takes me about 5 pedal revolutions to accelerate up to about 28-30 mph. I'd also argue that the acceleration, if I stayed in one gear, is about 5 revolutions, and at 90 rpms, that's just over 3 seconds.

    I'd also argue that by reducing the amount of time spent accelerating, the force required to make the change is different. If you want a slow acceleration, you need to input less power. Look at 0-60 times in cars - they all end up at 60 but some take 5 seconds, some 9. The differences include power, aerodynamics, and weight. Given a certain body/shape/etc (say a popular car like the bmw 3 series), you can get different engine options. The powerful ones allow the car to accelerate quicker and the car is otherwise essentially the same. Likewise, reducing acceleration times significantly increases power demand for acceleration. This in turn will be more affected by, say, less rotating weight.

    I think there's some kind of correlation between aero and weight for bike racing needs. The weight line starts high (significant) at low speeds and tapers down as speed increases. The aero line starts low (insignificant) at low speeds but dramatically curves up at about 25-30 mph field speed (i.e. even with drafting it's significant). Where the lines cross is where one should select weight vs aero.

    I'll have to find a physicist to explain to me if I'm way off base or not. I was never good at proofs.

    Ultimately, I find that if accelerating from lower speeds (teens in mph, some corners require slowing to 15 mph even if you're leading through the turn), light wheels make a huge difference. If accelerating from high speeds (over, say, 25 mph), aero wheels make it easier on me. I have to think that there is some factor or calculation which will show this to be the case, but I'm afraid I'm not educated enough to be able to prove it. arg.

    too dumb to prove it,
    cdr
    "...during the Lance years, being fit became the No. 1 thing. Totally the only thing. It’s a big part of what we do, but fitness is not the only thing. There’s skills, there’s tactics … there’s all kinds of stuff..." Tim Johnson

  22. #22
    Making a kilometer blurry waterrockets's Avatar
    Join Date
    May 2006
    Location
    Austin (near TX)
    My Bikes
    rkwaki's porn collection
    Posts
    26,029
    Mentioned
    19 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Yoshi View Post
    So what you're saying is that it only takes 7 watts to go from 36mph to 43mph when you're sprinting? Because if you believe that you're only saving 2 watts, then you also believe that it only takes 7 watts of power to sprint.

    Obviously it takes a lot more wattage to go from 36 to 43mph in 7 seconds. Likewise, you are going to save a lot more than 2 watts by dropping 412g. Assuming a linear curve (which it almost definitely isn't), if it took you a 500 watt increase to accelerate from 36-43mph dropping 412g would mean you'd only need a 357 watt increase to go from 36-43mph.

    Of course the relationship is far from linear so you wouldn't save 143 watts, but you'd definitely save far more than 2.
    Personally, I think it takes close to 1500W to do this

    Yeah, like DrWJ said, all I'm trying to measure is the effect of rotating mass on bicycle acceleration. What I found is that it takes around 2W to accelerate my tube and tire from ~450rpm to ~550rpm. Then I said that this rotating mass is similar to the difference between a pair of Zipp 404s vs Velocity Deep-Vs.

    The 1-second interval in the PT combined with the speed reading lag are far from ideal for this test, but the system does respond at this level. If I spin up really fast from a standstill, I get about 50W, so it's not like it's always going to get single-digits or anything.

    I have not done an error analysis on this, but I feel I've made a decent argument that rotating weight in bicycle wheels has a very very small impact on performance. Compared to aerodynamics with deep section rims, rotating weight is irrelevant.
    Last edited by waterrockets; 12-07-07 at 02:46 PM.

  23. #23
    Senior Member
    Join Date
    Feb 2007
    Posts
    3,918
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by fuhrermatt View Post
    Yeah, I agree with the whole weight weenie thing, but 2.2 lbs off wheels is huge. And like others have said, since its a rotational mass, it will be far more noticeable than 2.2 lbs of your gut.
    It really depends......


    If you lost the 2.2lbs from your gut but kept the same power output (or even increased power due to better fitness) the weight loss from your gut wins.

  24. #24
    Senior Member
    Join Date
    Feb 2007
    Posts
    3,918
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by waterrockets View Post
    Personally, I think it takes close to 1500W to do this

    Yeah, like DrWJ said, all I'm trying to measure is the effect of rotating mass on bicycle acceleration. What I found is that it takes around 2W to accelerate my tube and tire from ~450rpm to ~550rpm. Then I said that this rotating mass is similar to the difference between a pair of Zipp 404s vs Velocity Deep-Vs.

    The 1-second interval in the PT combined with the speed reading lag are far from ideal for this test, but the system does respond at this level. If I spin up really fast from a standstill, I get about 50W, so it's not like it's always going to get single-digits or anything.

    I have not done an error analysis on this, but I feel I've made a decent argument that rotating weight in bicycle wheels has a very very small impact on performance. Compared to aerodynamics with deep section rims, rotating weight is irrelevant.
    Clearly you must test this on the road... ride once with a tire and once without... report back the findings.

  25. #25
    Senior Member
    Join Date
    Nov 2004
    Posts
    2,544
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    nevermind.

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •